Orthostatic hypotension is experienced when a person sits or stands up following a prolonged rest period in a horizontal or supine position. Orthostasis means upright posture, and hypotension means low blood pressure. During such a change in posture, the cardiovascular system may make rapid adjustments to increase blood pressure and heart rate. When such adjustments are not made, orthostatic hypotension may occur. Orthostatic hypotension is commonly defined as a decrease of at least 20 mm Hg in systolic blood pressure and/or a 10 mm Hg drop in diastolic blood pressure when an individual moves from the horizontal to upright position.
The symptoms of orthostatic hypotension include dizziness, faintness, or lightheadedness that manifest when changing positions from lying to sitting or standing. Other symptoms that often accompany orthostatic hypotension include chest pain, trouble holding urine, impotence, and dry skin from loss of sweating. Some patients with severe orthostatic hypotension are severely incapacitated.
Implantable cardiac stimulation devices, such as pacemakers, have been used to combat orthostatic hypotension. As the use of such devices is still relatively new, there is ongoing research concerning the effectiveness of current pacing therapies on orthostatic hypotension. One research report produced by researchers Shibgilla and colleagues examined changes in blood pressure of pacemaker patients in response to upward tilts of the patients. First, the researchers screened out pacemaker patients whose rhythm upon standing was, with their standard programmed pacemaker settings, intrinsic (only 26% of patients). Next, the patients who were paced upon standing (74%) were subjected to multiple tilts, each with their pacemaker set to various base rates and pacing configuration settings. Perhaps surprisingly, the researchers found that the transient blood pressure drop upon tilt was smallest when patients were set to slower base rates (e.g., VVI 40 bpm, the slowest test base rate setting where patients were in their intrinsic rhythm). All other base rate settings (e.g., 60–90 bpm) in either AAI, VVI, or DDD modes, during which the patients were paced throughout the tilt, yielded greater transient drops in blood pressure. Interestingly, the intrinsic rates that were mostly achieved by patients upon tilt were less than 60 bpm. See, Dr. med. Volker Schibgilla, “Influence of Artificial Cardiac Pacing on Cardiovascular Regulation of Pacemaker Patients: Significance and Therapeutic Implications”, Medical Clinic II (Cardiology) with Teaching Hospital of the University of Erlangen-Nuremberg (Director: Prof. Dr. med. K. Bachmann), Habilitation Thesis of the Faculty of Medicine of the Friedrich Alexander University Erlangen-Nuremberg, 1997.
Research such as the Shibgilla report continues to fuel ongoing needs for improved techniques aimed at reducing the transient blood pressure drop upon orthostasis.